Recently, developments have been made on ferroelectric random access memories (FeRAM) configured to retain information in ferroelectric capacitors by utilizing polarization inversion of ferroelectrics. A ferroelectric memory is drawing attention particularly because it is a non-volatile memory which does not lose retained information even after power is turned off, and is capable of achieving a high degree of integration, high-speed drive, high durability, and low power consumption.
The ferroelectric capacitor is formed by sequentially forming a lower electrode, a capacitor dielectric film made of a ferroelectric material, and an upper electrode in this order.
Among them, the upper electrode influences a ferroelectric property of the capacitor dielectric film and various types of structures for the upper electrode have been reported.
A related art is disclosed in Japanese Laid-open Patent Publication Nos. 2007-103875, 2003-133531, 2002-299576, Hei 11-40748, and International Publication Pamphlet No. WO98/06131.